When it came to sex, dinosaurs had a hard time:
The plated, spiked stegosaurs are perhaps the most perplexing paramours of all. Consider Kentrosaurus, a cousin of the more famous Stegosaurus. This armored dinosaur sported huge spikes on its lower back and hips that must have looked dangerous to males in the mood. I asked my paleontologist friend Heinrich Mallison of the Museum of Natural History in Berlin to evaluate the possibility that Kentrosaurus mated in the leg-over-back position using computer models he had previously developed to study how flexible the animal was. Mallison tested dinosaur sex positions in three dimensions and concluded that the traditional dinosaur sex position did not work for Kentrosaurus. If a male tried to throw his leg over the back of a crouching female, he would castrate himself on her sharp spikes. One hip spike in particular seemed to be placed to strike fear in the hearts of stegosaur suitors.
Recent Dish on the kinks of the animal kingdom here.
The Dish 